This invention relates to systems and methods for inductive heating, and more specifically to power supplies for enhanced efficiency in such heating systems and methods.
It is common practice to inductively heat a cylinder or tube of a magnetisable material, such as steel, by an induction (eddy) current. This eddy current is induced in the material by an applied magnetic flux, the magnetic flux being generated by passage of an alternating current through one or more heater coils typically disposed around the cylinder or tube. This method of inductive heating can be adapted to various other types of work pieces or loads, including: fluids; filled or semisolid or solid materials (e.g., molten steel or magnesium filled and non-filled polymers, billets, ceramics); and substrates (e.g., where heat inductively generated in the substrate is transferred to another article, such as a semiconductor wafer).
In the various known systems, the article to be heated may itself be heated by an induction current, or the article to be heated may be in thermal communication, e.g., by conduction or radiation, with another article being inductively heated. Still further, the heater coil (to which the alternating current is applied, causing the coil to generate the alternating magnetic field) may be made of a more highly resistive material thereby increasing the amount of resistive heat generated in the coil; this resistive heat may likewise be transferred to the article to be heated. For example, Nichrome is a nickel chromimum (NiCr) alloy that has roughly sixty times the electrical resistivity of copper. Thus, a Nichrome heater coil can generate both an alternating magnetic field to cause inductive heating in an article lying within the field, as well as resistive heat in the coil which is then transferred by conduction and/or radiation to the same article.
Various systems have been proposed which utilize different combinations of such heating techniques. There is a need for energy sources to power such systems more efficiently and preferably at a lower cost than in the past.